Flexible aminoplast-curable film-forming compositions providing films having resistance to acid etching

ABSTRACT

A flexible, aminoplast-curable film-forming composition and a process for preparing multi-layered coated articles coated with a pigmented or colored base coat and a transparent or clear topcoat are disclosed. A pigmented or colored base coat is first applied to a substrate followed by the application of a transparent topcoat to the base coat. The transparent topcoat composition is a flexible, curable film-forming composition comprising (i) a polyether polymer containing a plurality of terminal or pendant carbamate groups of the structure: ##STR1## (ii) a polymer selected from the group consisting of a polyester polymer, a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure depicted above; and (iii) an aminoplast crosslinking agent. In a particularly preferred embodiment, the film-forming composition contains a polyester polymer derived from a cycloaliphatic acid or anhydride. The topcoat composition provides a flexible composite coating with improved acid etch resistance, making the composite coating particularly useful as a topcoat for plastic automotive parts.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 08/236,912, filed on Apr. 29, 1994, now abandoned. Reference is made to related U.S. patent applications Ser. Nos. 07/968,807, filed on Oct. 30, 1992, pending; 08/310,793, filed Oct. 7, 1994, pending; 08/329,915, filed Oct. 27, 1994, pending; and 08/345,918, filed Nov. 28, 1994, pending.

FIELD OF THE INVENTION

The present invention relates to flexible, aminoplast-curable film-forming compositions, and a process for preparing multi-layered coated articles comprising a pigmented or colored base coat and a transparent or clear topcoat.

BACKGROUND OF THE INVENTION

Plastic substrates are commonly used in automotive parts and accessories. Organic coating compositions are very often applied to these substrates for decorative and protective purposes. These plastic substrates are made of a variety of flexible thermosetting and thermoplastic materials such as polyethylene and polypropylene, thermoplastic urethane, polycarbonate, thermosetting sheet molding compound, reaction-injection molding compound, acrylonitrile-based materials, nylon and the like. The coating compositions that are used on these substrates must also be flexible so as to avoid cracking and adhesive failure under normal stresses and torsional forces to which the substrates may be subjected.

Color-plus-clear coating systems involving the application of a colored or pigmented base coat to a substrate followed by the application of a transparent or clear topcoat to the base coat have become conventional as original finishes for automobiles. The color-plus-clear systems have outstanding gloss and distinctness of image, and the clear coat is particularly important for these properties.

Aminoplast-cured coating systems are also well known and provide many excellent coating properties. They are inexpensive, durable, and attractive. However, it is widely recognized that such coatings, particularly clear coats, have poor resistance to etching by acid. Because many geographic areas encounter acidic precipitation, acid etch resistance in coatings is becoming an increasingly desirable property, particularly for automotive coatings. Coating systems of the prior art are not highly effective for providing protection against etching caused by acid rain.

Coating systems of the prior art which are known to be resistant to acid etch include acid-epoxy curable compositions such as those disclosed in U.S. Pat. No. 4,681,811 and compositions containing hydroxyl functional polymers reacted with isocyanates or polyisocyanates to form polyurethanes. The isocyanates are expensive and the toxicity of the isocyanates is an additional drawback.

It is desirable to provide an inexpensive, flexible coating composition for use on flexible automotive substrates using aminoplast curing agents which can be used in a color-plus-clear composite coating system having improved acid etch resistance properties and durability.

SUMMARY OF THE INVENTION

In accordance with the present invention, a flexible, curable film-forming composition is provided comprising (i) a polyether polymer containing a plurality, preferably up to about two, of terminal or pendant carbamate groups of the structure: ##STR2## (ii) a polymer selected from the group consisting of a polyester polymer, a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure depicted above; and (iii) an aminoplast crosslinking agent. In a particularly preferred embodiment, the film-forming composition contains a polyester polymer derived from a cycloaliphatic acid or anhydride.

A process for applying a composite coating to a substrate, preferably a plastic substrate, is also provided. The process comprises applying to the substrate a film-forming composition to form a base coat and applying to the base coat a clear film-forming composition to form a transparent topcoat over the base coat. The transparent topcoat, or clear coat, is derived from a flexible, curable film-forming composition comprising (i) a polyether polymer containing a plurality, preferably up to about two, of terminal or pendant carbamate groups of the structure: ##STR3## (ii) a polymer selected from the group consisting of a polyester polymer, a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure depicted above; and (iii) an aminoplast crosslinking agent.

DETAILED DESCRIPTION

The polyether polymer mentioned above may be prepared by reacting a polyether polyol with urea. More typically, the polyether polymer is prepared by a transcarbamoylation reaction described more fully below.

Examples of polyether polyols a repolyalkylene ether polyols which include those having the following structural formula: ##STR4## where the substituent R is hydrogen or lower alkyl containing from 1 to 5 carbon atoms including mixed substituents, and n is typically from 2 to 6 and m is from 8 to 100 or higher. Included are poly(oxytetramethylene) glycols, poly(oxytetraethylene) glycols, poly(oxy-1,2-propylene) glycols, and poly(oxy-1,2-butylene) glycols.

Also useful are polyether polyols formed from oxyalkylation of various polyols, for example, glycols such as ethylene glycol, 1,6-hexanediol, Bisphenol A and the like, or other higher polyols such as trimethylolpropane, pentaerythritol and the like. Polyols of higher functionality which can be utilized as indicated can be made, for instance, by oxyalkylation of compounds such as sucrose or sorbitol. One commonly utilized oxyalkylation method is reaction of a polyol with an alkylene oxide, for example, propylene or ethylene oxide, in the presence of an acidic or basic catalyst.

Preferred polyethers include those sold under the names TERATHANE and TERACOL, available from E. I. Du Pont de Nemours and Company, Inc.

Preferably, pendant carbamate functional groups may be incorporated into the polyethers by a "transcarbamoylation" reaction. In this reaction, a low molecular weight carbamate functional material derived from an alcohol or glycol ether is reacted with the hydroxyl groups of the polyether polyol, yielding a carbamate functional polyether and the original alcohol or glycol ether. The low molecular weight carbamate functional material derived from an alcohol or glycol ether is first prepared by reacting the alcohol or glycol ether with urea in the presence of a catalyst. Suitable alcohols include lower molecular weight aliphatic, cycloaliphatic, and aromatic alcohols such as methanol, ethanol, propanol, butanol, cyclohexanol, 2-ethylhexanol, and 3-methylbutanol. Suitable glycol ethers include ethylene glycol methyl ether and propylene glycol methyl ether. Propylene glycol methyl ether is preferred.

The polyether polymer preferably has a number average molecular weight of from about 500 to 5000, more preferably from about 1100 to 3200 as determined by gel permeation chromatography using a polystyrene standard, and an equivalent weight of within the range of 140 to 2500, preferably about 500, based on equivalents of reactive pendant or terminal carbamate groups. The equivalent weight is a calculated value based on the relative amounts of the various ingredients used in making the polyether polymer and is based on solids of the polyether polymer. Preferably, the pendant or terminal carbamate groups only have the structure depicted above.

The polyether polymer is typically present in the film-forming composition in amounts of about 5 to 50, preferably about 5 to 40, and more preferably about 10 to 30 percent by weight based on weight of resin solids in the film-forming composition.

Preferably, the film-forming composition further comprises a polymer selected from the group consisting of a polyester polymer, a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR5## This polymer or mixture of polymers (not including the polyether polymer) is used in amounts up to 60, preferably 5 to 50 percent by weight based on weight of resin solids in the film-forming composition, depending on the particular polymer or mixture of polymers used.

The acrylic polymers are copolymers of one or more alkyl esters of acrylic acid or methacrylic acid, and, optionally, one or more other polymerizable ethylenically unsaturated monomers. Suitable alkyl esters of acrylic or methacrylic acid include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Suitable other polymerizable ethylenically unsaturated monomers include vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride and vinyl esters such as vinyl acetate. The acrylic polymers may contain hydroxyl functionality which can be incorporated into the acrylic polymer through the use of hydroxyl functional monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate which may be copolymerized with the other acrylic monomers.

The acrylic polymer may be prepared by solution polymerization techniques in the presence of suitable initiators such as organic peroxides or azo compounds, for example, benzoyl peroxide or N,N-azobis(isobutyronitrile). The polymerization may be carried out in an organic solution in which the monomers are soluble by techniques conventional in the art.

Pendant carbamate functional groups may be incorporated into the acrylic polymer by copolymerizing the acrylic monomers with a carbamate functional vinyl monomer, for example a carbamate functional alkyl ester of methacrylic acid. These carbamate functional alkyl esters are prepared by reacting, for example, a hydroxyalkyl carbamate, such as the reaction product of ammonia and ethylene carbonate or propylene carbonate, with methacrylic anhydride. Other carbamate functional vinyl monomers are, for instance, the reaction product of hydroxyethyl methacrylate, isophorone diisocyanate, and hydroxypropyl carbamate. Still other carbamate functional vinyl monomers may be used, such as the reaction product of isocyanic acid (HNCO) with a hydroxyl functional acrylic or methacrylic monomer such as hydroxyethyl acrylate, and those described in U.S. Pat. No. 3,479,328. Pendant carbamate groups can also be incorporated into the acrylic polymer by reacting a hydroxyl functional acrylic polymer with a low molecular weight carbamate functional material via a transcarbamoylation process similar to the one described above in connection with the incorporation of carbamate groups into the polyethers.

The acrylic polymer typically has a number average molecular weight of from about 900 to 13,000, preferably from about 1000 to 5000 as determined by gel permeation chromatography using a polystyrene standard, and a carbamate equivalent weight less than 5000, preferably within the range of 140 to 2500, based on equivalents of reactive pendant or terminal carbamate groups. The equivalent weight is a calculated value based on the relative amounts of the various ingredients used in making the acrylic material and is based on solids of the acrylic polymer.

The acrylic polymer, when present in the film-forming composition, is used in amounts up to 50, preferably 5 to 15 percent by weight based on weight of resin solids in the film-forming composition.

Linear or branched polyesters may also be used in the formulation of the film-forming composition and may be prepared by the polyesterification of a polycarboxylic acid or anhydride thereof with polyols and/or an epoxide. Usually, the polycarboxylic acids and polyols are aliphatic or aromatic dibasic acids and diols. Transesterification of polycarboxylic acid esters is also possible.

The polyols which are usually employed in making the polyester include alkylene glycols, such as ethylene glycol, neopentyl glycol and other glycols, such as hydrogenated Bisphenol A, cyclohexanediol, cyclohexanedimethanol, caprolactonediol, for example, the reaction product of epsilon-caprolactone and ethylene glycol, hydroxy-alkylated bisphenols, polyether glycols, for example, poly(oxytetramethylene) glycol and the like. Polyols of higher functionality may also be used. Examples include trimethylolpropane, trimethylolethane, pentaerythritol and the like. Branched polyols such as trimethylolpropane are preferred.

The acid component of the polyester consists primarily of monomeric carboxylic acids or anhydrides thereof having 2 to 18 carbon atoms per molecule. Among the acids which are useful are cycloaliphatic acids and anhydrides such as phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, 1,3-cyclohexane dicarboxylic acid, and 1,4-cyclohexane dicarboxylic acid. Other suitable acids include adipic acid, azelaic acid, sebacic acid, maleic acid, glutaric acid, decanoic diacid, dodecanoic diacid and other dicarboxylic acids of various types. Lower alkyl diacids, that is, acids having less than about 10 carbon atoms such as adipic acid, are preferred. The polyester may include minor amounts of monobasic acids such as benzoic acid, stearic acid, acetic acid, and oleic acid. Also, there may be employed higher carboxylic acids such as trimellitic acid and tricarballylic acid. Where acids are referred to above, it is understood that anhydrides thereof which exist may be used in place of the acid. Also, lower alkyl esters of diacids such as dimethyl glutarate and dimethyl terephthalate may be used. Cycloaliphatic acids and anhydrides are particularly preferred. Though not intending to be bound by any particular theory, it is believed that the use of polyester polymers derived from cycloaliphatic acids and anhydrides improves the durability of the film-forming composition.

Pendant carbamate functional groups may be incorporated into the polyester by first forming a hydroxyalkyl carbamate which can be reacted with the polyacids and polyols used in forming the polyester. An example of a hydroxyalkyl carbamate is the reaction product of ammonia and ethylene carbonate or propylene carbonate. The hydroxyalkyl carbamate is condensed with acid functionality on the polyester, yielding pendant carbamate functionality. Pendant carbamate functional groups may also be incorporated into the polyester by reacting a hydroxyl functional polyester with a low molecular weight carbamate functional material via a transcarbamoylation process similar to the one described above in connection with the incorporation of carbamate groups into the polyethers, or by reacting isocyanic acid with a hydroxyl functional polyester.

The polyester polymer typically has a number average molecular weight of from about 500 to 2500, preferably from about 800 to 2100 as determined by gel permeation chromatography using a polystyrene standard, and a carbamate equivalent weight within the range of 200 to 1500, preferably about 200 to 500, based on equivalents of reactive pendant or terminal carbamate groups. The equivalent weight is a calculated value based on the relative amounts of the various ingredients used in making the polyester and is based on solids of the polyester.

The polyester polymer, when present in the film-forming composition, is used in amounts up to about 60, preferably about 20 to 50 percent by weight based on weight of resin solids in the film-forming composition. When the polyester polymer is derived from a cycloaliphatic acid or anhydride, the polyether polymer in the film-forming composition is present in amounts of about 5 to 50 percent by weight based on weight of resin solids in the film-forming composition.

Polyurethanes and urethane oligomers can also be used in the film-forming composition of the present invention. Among the polyurethanes which can be used are polymeric polyurethane which are prepared by reacting the polyester polyols or acrylic polyols such as those mentioned above with a polyisocyanate such that the OH/NCO equivalent ratio is greater than 1:1 so that free hydroxyl groups are present in the product.

The organic polyisocyanate which is used to prepare the polyurethane polyol can be an aliphatic or an aromatic polyisocyanate or a mixture of the two. Diisocyanates are preferred, although higher polyisocyanates can be used in place of or in combination with diisocyanates.

Examples of suitable aromatic diisocyanates are 4,4'-diphenylmethane diisocyanate and toluene diisocyanate. Examples of suitable aliphatic diisocyanates are straight chain aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates can be employed. Examples include isophorone diisocyanate and 4,4'-methylene-bis-(cyclohexyl isocyanate). Examples of suitable higher polyisocyanates are 1,2,4-benzene triisocyanate and polymethylene polyphenyl isocyanate.

Pendant carbamate functional groups may be incorporated into the polyurethane by reacting a polyisocyanate with a polyester polyol containing the pendant carbamate groups. Alternatively, the pendant carbamate functional groups may be incorporated into the polyurethane by reacting a polyisocyanate with a polyester polyol and a hydroxyalkyl carbamate or isocyanic acid as separate reactants. Pendant carbamate functional groups may also be incorporated into the polyurethane by reacting a hydroxyl functional polyurethane with a low molecular weight carbamate functional material via a transcarbamoylation process similar to the one described above in connection with the incorporation of carbamate groups into the polyethers.

The polyurethane typically has a number average molecular weight of from about 300 to 3000, preferably from about 300 to 600 as determined by gel permeation chromatography using a polystyrene standard, and a carbamate equivalent weight within the range of 140 to 2600, based on equivalents of reactive pendant or terminal carbamate groups. The equivalent weight is a calculated value based on the relative amounts of the various ingredients used in making the polyurethane and is based on solids of the polyurethane.

The polyurethane polymer, when present in the film-forming composition, is used in amounts up to 50, preferably up to 20 percent by weight based on weight of resin solids in the film-forming composition.

Among the urethane oligomer adducts are the reaction products of diisocyanate and hydroxyalkyl carbamates, wherein the alkyl group can have from 2 to 10 carbons. An example is the reaction product of isophone diisocyanate and hydroxypropyl carbamate and/or hydroxyethylcarbamate.

The coating composition also includes an aminoplast crosslinking agent containing methylol and/or methylol ether groups. Aminoplasts are obtained from the reaction of formaldehyde with an amine or amide. The most common amines or amides are melamine, urea, or benzoguanamine, and are preferred. However, condensates with other amines or amides can be used; for example, aldehyde condensates of glycoluril, which give a high melting crystalline product which is useful in powder coatings. While the aldehyde used is most often formaldehyde, other aldehydes such as acetaldehyde, crotonaldehyde, and benzaldehyde may be used.

The aminoplast contains methylol groups and preferably at least a portion of these groups are etherified with an alcohol to modify the cure response. Any monohydric alcohol may be employed for this purpose including methanol, ethanol, butanol, and hexanol.

Preferably, the aminoplasts which are used are melamine-, urea-, or benzoguanamine-formaldehyde condensates etherified with an alcohol containing from one to four carbon atoms. The aminoplast is present in amounts of about 15 to 50, preferably 20 to 35 percent by weight based on weight of resin solids in the film-forming composition.

In the coating composition of the present invention, preferably the equivalent ratio of the pendant or terminal carbamate groups in the polymers to methylol or methylol ether groups in the aminoplast is from 0.5 to 2:1 and is sufficient to form a crosslinked film.

Preferably, prior to crosslinking, the film-forming composition comprising the polymer(s) having the pendant or terminal carbamate groups and the aminoplast has a theoretical hydroxyl value less than 50, preferably less than 25, and more preferably 0, based on solid weight of the film-forming composition, excluding any hydroxyl functionality associated with N-methylol groups such as those in an aminoplast.

By "theoretical hydroxyl value" is meant the calculated value based on the relative amounts of the various ingredients used in making the film-forming composition, rather than the actual hydroxyl value which is measured on the film-forming composition itself by conventional analytical techniques. The resultant crosslinked coating contains a substantial number of urethane crosslinks which arise from reaction of the terminal or pendant carbamate groups with the aminoplast, thereby providing a high level of acid etch resistance.

The film-forming composition of the present invention is preferably used as the clear coat layer in a "color-plus-clear" coating system. The film-forming composition of the base coat in the color-plus-clear system can be any of the compositions useful in coatings applications, particularly automotive applications. The film-forming composition of the base coat comprises a resinous binder and a pigment to act as the colorant. Particularly useful resinous binders are acrylic polymers, polyesters, including alkyds, and polyurethanes.

The base coat compositions may be solventborne or waterborne. Water-based base coats in color-plus-clear compositions are disclosed in U.S. Pat. No. 4,403,003, and the resinous compositions used in preparing these base coats can be used in the practice of this invention. Also, water-based polyurethanes such as those prepared in accordance with U.S. Pat. No. 4,147,679 can be used as the resinous binder in the base coat. Further, water-based coatings such as those described in U.S. Pat. No. 5,071,904 can be used as the base coat.

The base coat also contains pigments to give it color. Compositions containing metallic flake pigmentation are useful for the production of so-called "glamour metallic" finishes chiefly upon the surface of automobile bodies. Suitable metallic pigments include in particular aluminum flake, copper bronze flake and metal oxide coated mica.

Besides the metallic pigments, the base coating compositions of the present invention may contain non-metallic color pigments conventionally used in surface coatings including inorganic pigments such as titanium dioxide, iron oxide, chromium oxide, lead chromate, and carbon black, and organic pigments such as phthalocyanine blue and phthalocyanine green. In general, the pigment is incorporated into the coating composition in amounts of about 1 to 80 percent by weight based on weight of coating solids. The metallic pigment is employed in amounts of about 0.5 to 25 percent by weight based on weight of coating solids.

If desired, the base coat composition may contain additional materials well known in the art of formulated surface coatings. These would include surfactants, flow control agents, thixotropic agents, fillers, anti-gassing agents, organic cosolvents, catalysts, and other customary auxiliaries. These materials can constitute up to 40 percent by weight of the total weight of the coating composition.

The base coating compositions can be applied to various substrates to which they adhere. The compositions can be applied by conventional means including brushing, dipping, flow coating, spraying and the like, but they are most often applied by spraying. The usual spray techniques and equipment for air spraying and electrostatic spraying and either manual or automatic methods can be used.

Although the coatings of the present invention may be applied to various substrates including wood, metals, and glass, they are particularly effective in applications over plastic substrates that are found on motor vehicles. By "plastic" is meant any of the common thermoplastic or thermosetting synthetic nonconductive materials, including thermoplastic olefins such as polyethylene and polypropylene, thermoplastic urethane, polycarbonate, thermosetting sheet molding compound, reaction-injection molding compound, acrylonitrile-based materials, nylon and the like.

During application of the base coat composition to the substrate, a film of the base coat is formed on the substrate. Typically, the base coat thickness will be about 0.01 to 5, preferably 0.1 to 2 mils in thickness.

After application of the base coat to the substrate, a film is formed on the surface of the substrate by driving solvent, i.e., organic solvent or water, out of the base coat film by heating or by an air drying period. Preferably, the heating will only be for a short period of time sufficient to ensure that the clear coat can be applied to the base coat without the former dissolving the base coat composition. Suitable drying conditions will depend on the particular base coat composition and on the ambient humidity with certain water-based compositions, but in general a drying time of from about 1 to 5 minutes at a temperature of about 80°-250° F. (20°-121° C.) will be adequate to ensure that mixing of the two coats is minimized. At the same time, the base coat film is adequately wetted by the clear coat composition so that satisfactory intercoat adhesion is obtained. Also, more than one base coat and multiple clear coats may be applied to develop the optimum appearance. Usually between coats, the previously applied coat is flashed; that is, exposed to ambient conditions for about 1 to 20 minutes.

As mentioned above, the clear film-forming composition will contain the carbamate functional polyether polymers and a carbamate functional polymer selected from the group consisting of a polyester polymer, a polyurethane polymer, an acrylic polymer, and mixtures thereof as well as an aminoplast crosslinking agent. Usually, the clear film-forming composition will also preferably contain catalysts to accelerate the cure of the aminoplast and pendant carbamate groups. Examples of suitable catalysts are acidic materials and include acid phosphates and sulfonic acid or a substituted sulfonic acid such as dodecylbenzene sulfonic acid or paratoluene sulfonic acid. The catalyst is usually present in an amount of about 0.5 to 5.0 percent by weight, preferably about 1 to 2 percent by weight, based on weight of total resin solids. Optional ingredients such as, for example, plasticizers, flow controllers, anti-oxidants, UV light absorbers and similar additives conventional in the art may be included in the composition. These ingredients are typically present at up to 25% by weight based on total resin solids.

The clear topcoat composition may be applied to the base coated substrate by any conventional coating technique such as brushing, spraying, dipping or flowing, but spray applications are preferred because of superior gloss. Any of the known spraying techniques may be employed such as compressed air spraying, electrostatic spraying and either manual or automatic methods.

After application of the clear coat composition to the base coat, the coated substrate is heated to cure the coating layers. In the curing operation, solvents are driven off and the film-forming materials of the clear coat and the base coat are each crosslinked. The heating or curing operation is usually carried out at a temperature in the range of from 160°-350° F. (71°-177° C.) but if needed, lower or higher temperatures may be used as necessary to activate crosslinking mechanisms. The thickness of the clear coat is usually from about 0.5-5, preferably 1.2-3 mils.

The invention will further be described by reference to the following examples. Unless otherwise indicated, all parts are by weight. Examples A through I illustrate the preparation of various polymers with and without carbamate functionality.

EXAMPLE A

A carbamate functional polyether was prepared from the following ingredients:

    ______________________________________                                         Ingredient        Weight in grams                                              ______________________________________                                         TERATHANE 650.sup.1                                                                              1300.00                                                      Propylene glycol methyl ether                                                                    526.3                                                        (DOWANOL PM) carbamate.sup.2                                                   butyl stannoic acid (BSA)                                                                        1.83                                                         triphenylphosphite (TPP)                                                                         1.83                                                         ______________________________________                                          .sup.1 Polytetramethylene glycol, available from E. I. Du Pont de Nemours      and Company, Inc., having a number average molecular weight of 600 to 700      and an OH value of 160 to 187.                                                 .sup.2 Reaction product of Propylene glycol methyl ether (available from       Dow Chemical Co. as DOWANOL PM) and urea, 96.9% in DOWANOL PM            

A suitable reactor equipped for vacuum distillation was charged with the above ingredients and heated to 100° C. under a N₂ blanket. The reaction mixture was sparged with N₂ for 20 minutes at this temperature. Upon completion of sparging, the temperature of the reaction mixture was raised to 140° C. Vacuum was applied to the system until DOWANOL PM began to distill from the reaction mixture. The vacuum on the system was gradually increased as the reaction progressed to a maximum vacuum of 1 mm to maintain a steady distillation of DOWANOL PM. The resultant reaction mixture was a soft, white, waxy opaque material with a OH value of 12.9, a total N content of 3.67%, and a number average molecular weight of 1192 as determined by gel permeation chromatography using a polystyrene standard. The calculated carbamate equivalent weight was 386.

EXAMPLE B

A carbamate functional polyether was prepared from the following ingredients:

    ______________________________________                                         Ingredient        Weight in grams                                              ______________________________________                                         POLYMEG 1000.sup.1                                                                               2000.00                                                      DOWANOL FM carbamate                                                                             524.4                                                        butyl stannoic acid                                                                              2.51                                                         triphenylphosphite                                                                               2.51                                                         ______________________________________                                          .sup.1 polytetramethylene glycol, having a number average molecular weigh      of about 1000, available from Q O Chemicals, Inc., a subsidiary of Great       Lakes Chemical Corp.                                                     

A suitable reactor equipped for vacuum distillation was charged with the above ingredients and heated to 100° C. The reaction mixture was sparged with N₂ for 20 minutes at this temperature. Upon completion of sparging, the temperature of the reaction mixture was raised to 140° C. Vacuum was applied to the system until DOWANOL PM began to distill from the reaction mixture. The vacuum on the system was gradually increased as the reaction progressed to a maximum vacuum of 1 mm in order to maintain a steady distillation of DOWANOL PM. The resultant reaction mixture was a soft, white, waxy opaque material with an OH value of 15.4, a total N content of 3.67%, and a number average molecular weight of 1748 as determined by gel permeation chromatography using a polystyrene standard. The calculated carbamate equivalent weight was 571.

EXAMPLE C

A carbamate functional polyether was prepared from the following ingredients:

    ______________________________________                                         Ingredient       Weight in grams                                               ______________________________________                                         TERATHANE 2000.sup.1                                                                            2000.00                                                       DOWANOL PM carbamate                                                                            263.15                                                        butyl stannoic acid                                                                             2.27                                                          triphenylphosphite                                                                              2.27                                                          ______________________________________                                          .sup.1 Polytetramethylene glycol, available from E. I. Du Pont de Nemours      and Company, Inc., having a number average molecular weight of 1900 to         2100 and an OH value of 53 to 59.                                        

A suitable reactor equipped for vacuum distillation was charged with the above ingredients and heated to 100° C. The reaction mixture was sparged with N₂ for 20 minutes at this temperature. Upon completion of sparging, the temperature of the reaction mixture was raised to 140° C. Vacuum was applied to the system until DOWANOL PM began to distill from the reaction mixture. The vacuum on the system was gradually increased as the reaction progressed to a maximum vacuum of 1 mm to maintain a steady distillation of DOWANOL PM. The resultant reaction mixture was a soft, slightly yellow, waxy opaque material with an OH value of 5.4, a total N content of 1.3%, and a number average molecular weight of 3127 as determined by gel permeation chromatography using a polystyrene standard. The calculated carbamate equivalent weight was 1095.

EXAMPLE D

A carbamate functional linear polyester urethane was prepared from the following ingredients:

    ______________________________________                                         Ingredient       Weight in grams                                               ______________________________________                                         polyester urethane polyol.sup.1                                                                 2348.4                                                        triphenylphosphite                                                                              2.35                                                          DOWANOL PM carbamate                                                                            744.66                                                        butyl stannoic acid                                                                             3.10                                                          triphenylphosphite                                                                              3.10                                                          ______________________________________                                          .sup.1 Reaction product of neopentyl glycol, hexahydrophthalic anhydride,      adipic acid, and 4,4methylenebis(cyclohexyl isocyanate) (available as          DESMODUR W from Miles, Inc.) in a 1.00:0.50:0.22:0.002 mole ratio, having      a hydroxyl value of 159.3 based on weight of resin solids, 90.0% in            DOWANOL PM acetate.                                                      

The first two ingredients were charged to a suitable reactor equipped for vacuum distillation and heated to 140° C. under a N₂ blanket. Vacuum was applied to the system and DOWANOL PM acetate solvent was removed from the pot under reduced pressure. The reaction was cooled to 80° C. and the remaining ingredients were added to the reactor. The reaction mixture was heated to 100° C. and sparged with nitrogen for 20 minutes at this temperature. Upon completion of sparging, the temperature of the reaction mixture was raised to 140° C. Vacuum was applied to the system until DOWANOL PM began to distill from the reaction mixture. The vacuum on the system was gradually increased as the reaction progressed to a maximum vacuum of 1 mm to maintain a steady distillation of DOWANOL PM. After the reaction was complete, the reaction product was thinned with 661 g DOWANOL PM acetate to a measured solids of 84.0% and a viscosity of Z5 on the Gardner-Holt scale. The thinned reaction product had an OH value of 18.5 based on resin solids, a number average molecular weight of 873, and a weight average molecular weight of 1292. The calculated carbamate equivalent weight was 479.

EXAMPLE E

A branched polyester derived from a cycloaliphatic anhydride was prepared from the following ingredients:

    ______________________________________                                         Ingredient          Weight in grams                                            ______________________________________                                         trimethylolpropane  900.4                                                      methylhexahydrophthalic anhydride                                                                  3326.4                                                     ESTERDIOL 204.sup.1 4124.8                                                     TPP                 8.34                                                       BSA                 12.54                                                      ______________________________________                                          .sup.1 2,2dimethyl-3-hydroxypropyl 2,2dimethyl-3 hydroxypropanoate,            available from Union Carbide Chemicals and Plastics Co., Inc.            

The above ingredients were charged to a suitable reactor, equipped with a N₂ sparge, a glycol recovery column and a distillation head, heated to 80° C., and degassed three times by pulling a vacuum on the reactor and backfilling with N₂. The reaction mixture was then heated to a temperature between 200° C. and 210° C. with removal of water. As water was removed from the reaction, the acid value dropped to 2.8. The final product was a transparent material with a viscosity >Z6 on the Gardner-Holt viscosity scale, a measured solids of 96.3%, an OH value of 125.4 based on resin solids, a number average molecular weight of 1254, and a weight average molecular weight of 2794.

EXAMPLE F

A carbamate functional branched polyester derived from a cycloaliphatic anhydride was prepared from the following ingredients:

    ______________________________________                                         Ingredient       Weight in grams                                               ______________________________________                                         polyester from Example E                                                                        3050.4                                                        DOWANOL PM carbamate                                                                            1034.03                                                       TPP              4.07                                                          BSA              4.07                                                          ______________________________________                                    

A reactor equipped for vacuum distillation was charged with the above ingredients and heated to 95° C. The reaction mixture was degassed three times at this temperature by evacuating the reactor and back-filling with N₂ each time. Upon completion of degassing, the temperature of the reaction mixture was raised to 140° C. Vacuum was applied to the system until DOWANOL PM began to distill from the reaction mixture. The vacuum on the system was gradually reduced as the reaction progressed to a maximum vacuum of 1 mm in order to maintain a steady distillation of DOWANOL PM. The resultant reaction mixture was a viscous, resinous material with an OH value of 8.8 and a measured solids of 98.7. After dilution with 1000 g n-propanol, the reaction mixture has a measured solids of 76.4%, a viscosity of Z1⁺ on the Gardner-Holt scale. The carbamate functional branched polyester had a number average molecular weight of 1349, a weight average molecular weight of 3131, and a total N content of 2.51%. The calculated carbamate equivalent weight was 386.

EXAMPLE G

A carbamate functional acrylic polymer was prepared from the following ingredients:

    ______________________________________                                         Ingredient       Weight in grams                                               ______________________________________                                         acrylic polymer.sup.1                                                                           2239.9                                                        DOWANOL PM carbamate                                                                            903.9                                                         TPP              3.11                                                          BSA              3.11                                                          ______________________________________                                          .sup.1 Reaction product of hydroxypropyl acrylate, styrene, butyl              acrylate, butyl methacrylate, methyl methacrylate, and methyl styrene          dimer in a 40:20:19:18.5:0.5:2 weightratio, approximately 10,000 weight        average molecular weight, stripped to 100% theory solids.                

A reactor equipped for vacuum distillation was charged with the above ingredients and heated to 100° C. The reaction mixture was sparged with N₂ for 20 minutes at this temperature. Upon completion of sparging, the temperature of the reaction mixture was raised to 140° C. Vacuum was applied to the system until DOWANOL PM began to distill from the reaction mixture. The vacuum on the system was gradually reduced as the reaction progressed to a maximum vacuum of 1 mm in order to maintain a steady distillation of DOWANOL PM. After the reaction was complete, the reaction mixture was thinned with a 1:1 blend of butyl acetate and AROMATIC 100 (also called SOLVESSO 100, available from Exxon Chemical Co.) to a theory solids of 70% and a final viscosity of >Z6 on the Gardner-Holt scale. The carbamate functional acrylic polymer had a total N content of 2.93%, a number average molecular weight of 4063, and a weight average molecular weight of 18,884. The calculated carbamate equivalent weight was 386.

EXAMPLE H

A branched carbamate functional polyester similar to the polyester of Example F but based on a linear diacid instead of a cycloaliphatic anhydride was prepared from the following ingredients:

    ______________________________________                                         Ingredients           Weight in grams                                          ______________________________________                                         trimethylolpropane    188.08                                                   sebacic acid          836.95                                                   2,2-dimethyl-3-hydroxypropyl-                                                                        861.70                                                   2,2-dimethyl-3-hydroxypropyl                                                   propionate                                                                     butyl stannoic acid   3.78                                                     triphenylphosphite    1.89                                                     butyl stannoic acid   2.48                                                     triphenylphosphite    2.48                                                     DOWANOL PM carbamate (37% solution                                                                   1573.3                                                   in DOWANOL PM)                                                                 DOWANOL PM            643.5                                                    ______________________________________                                    

The first five ingredients were charged to a suitable reactor equipped with a nitrogen sparge and a glycol recovery column and heated to 210° C. As water was removed from the reaction, the acid value of the reaction mixture dropped to 3.1. The intermediate resin was then cooled to 140° C. Butyl stannoic acid and triphenylphosphite were added to the reactor. DOWANOL PM carbamate in DOWANOL PM solution was added to the reactor over a period of three hours. During the addition, DOWANOL PM was removed from the reactor under reduced pressure. The reaction was continued until DOWANOL PM evolution stopped. Before dilution, the material had a residual OH value of 18.1. The resin was diluted with DOWANOL PM. After dilution, the resin had a measured solids content of 75.0%, a Gardner-Holt viscosity of V-, a number average molecular weight of 1688, and a weight average molecular weight of 6182 as determined by gel permeation chromatography using a polystyrene standard.

EXAMPLE I

A branched carbamate functional polyester derived from a cycloaliphatic anhydride was prepared from the following ingredients:

    ______________________________________                                         Ingredient            Weight in parts                                          ______________________________________                                         2,2-dimethyl-3-hydroxypropyl-                                                                        158.2                                                    2,2-dimethyl-3-hydroxypropyl propionate                                        deionized H.sub.2 O   7.0                                                      trimethylolpropane    69.4                                                     butyl stannoic acid   0.6                                                      triphenylphosphite    0.4                                                      deionized H.sub.2 O   3.0                                                      methylhexahydrophthalic anhydride                                                                    170.4                                                    DOWANOL PM            3.0                                                      butyl stannoic acid   0.5                                                      triphenylphosphite    0.5                                                      DOWANOL PM            2.0                                                      DOWANOL PM carbamate (37%                                                                            451.0                                                    solution in DOWANOL PM)                                                        DOWANOL PM            5.0                                                      DOWANOL PM            145.0                                                    ______________________________________                                    

The first ingredient was charged to a suitable reactor equipped with a glycol recovery column. Deionized H₂ O was added to the reactor as a rinse for the first ingredient. Trimethylolpropane, butyl stannoic acid, and triphenylphosphite were then added to the reactor, followed by a deionized water rinse. Methylhexahydrophthalic anhydride was then added to the reactor. The reaction mixture was then heated to 77° C. and sparged with nitrogen for 20 minutes. The reaction mixture was heated to 210° C. and water was removed from the reactor with the nitrogen sparge. The reaction was held to an acid value of 10.4 and the batch cooled to 140° C. The intermediate resin had a hydroxyl value of 164.5. DOWANOL PM and butyl stannoic acid were added to the reactor as a slurry, followed by addition of triphenylphosphite and a DOWANOL PM rinse. DOWANOL PM carbamate in DOWANOL PM solution was added to the reactor over a period of four hours. During the addition, DOWANOL PM was removed from the reactor under reduced pressure. Upon completion of the addition, a DOWANOL PM rinse was added to the reactor. The reaction was continued until DOWANOL PM evolution stopped. The resin prior to dilution had a residual hydroxyl value of 17.8 and an acid value of 7.9. After dilution, the resin had a measured solids content of 69.3%, a Gardner-Holt viscosity of Z3-, a number average molecular weight of 1197, and a weight average molecular weight of 3340 as determined by gel permeation chromatography using a polystyrene standard.

The following examples (1-10) show the preparation of various clear film-forming flexible compositions prepared with carbamate and/or hydroxyl functional materials and aminoplast curing agents. The coating compositions were evaluated in color-plus-clear applications.

EXAMPLE 1

A clear film-forming composition containing carbamate functional polyether, acrylic, and polyurethane polymers was prepared by mixing together the following ingredients:

    ______________________________________                                                           Solid weight                                                                               Solution weight                                  Ingredient        in grams    in grams                                         ______________________________________                                         Propylene glycol methyl ether                                                                    --          4.8                                              acetate                                                                        SOLVESSO 100      --          9.5                                              oxo-hexyl acetate --          10.3                                             n-propanol        --          15.0                                             xylene            --          9.0                                              TINUVIN 328.sup.1 3.0         3.0                                              AEROSIL R812 dispersion.sup.2                                                                    5.5         12.5                                             RESIMENE 741.sup.3                                                                               35.0        39.7                                             carbamate containing polyether of                                                                15.0        15.0                                             example B                                                                      carbamate containing acrylic polymer                                                             10.5        16.6                                             of example G                                                                   carbamate containing polyurethane of                                                             35.0        45.6                                             example D                                                                      DOW CORNING 200.sup.4                                                                            0.004       0.74                                             BYK 325.sup.5     0.02        0.13                                             Polybutylacrylate.sup.6                                                                          0.25        0.42                                             phenyl acid phosphate                                                                            0.15        0.2                                              Dodecylbenzene sulfonic acid                                                                     0.75        1.10                                             ______________________________________                                          .sup.1 Substituted benzotriazole UV light absorber available from Ciba         Geigy Corporation                                                              .sup.2 Eight parts by weight (pbw) of a highly dispersed hydrophobic           amorphous silicon dioxide available from Degussa Corporation; 50 pbw of a      solution of hydroxyl functional acrylic polymer having a peak molecular        weight of 8000, Mw of 9000, Mn of 3500 (determined by gel permeation           chromatography using a polystyrene standard) made from 40% hydroxypropyl       acrylate, 20% styrene, 19% butyl acrylate, 18.5% butyl methacrylate, 0.5%      methyl methacrylate, 2% acrylic acid at 70% solids in isobutanol, xylene,      and SOLVESSO 100; 48.75 pbw xylene; 1.5 pbw isobutanol; 6.75 pbw SOLVESSO      100.                                                                           .sup.3 Partially methylated aminoplast resin available from Monsanto           Chemical Company.                                                              .sup.4 Solution of polymethylsiloxane, available from Dow Corning              Corporation.                                                                   .sup.5 Solution of polyoxyalkylenemethylalkyl-polysiloxane copolymer           available from BykChemie.                                                      .sup.6 Flow contro1 agent having a Mw of about 6700 and a Mn of about          2600, made in xylene at 60% solids.                                      

EXAMPLE 2 (Control)

A clear film-forming composition analogous to Example 1, but containing only hydroxyl functional polymers, was prepared by mixing together the following ingredients:

    ______________________________________                                                          Solid weight Solution weight                                  Ingredient       in grams     in grams                                         ______________________________________                                         Propylene glycol methyl ether                                                                   --           4.8                                              acetate                                                                        SOLVESSO 100     --           9.5                                              oxo-hexyl acetate                                                                               --           10.3                                             n-propanol       --           15.0                                             xylene           --           9.0                                              TINUVIN 328      3.0          3.0                                              AEROSIL R812 dispersion                                                                         5.5          12.5                                             RESIMENE 741     35.0         39.7                                             POLYMEG 1000     15.0         15.0                                             Acrylic polymer.sup.1                                                                           10.5         16.6                                             Polyester urethane polyol.sup.2                                                                 35.0         45.6                                             DOW CORNING 200  0.004        0.74                                             BYK 325          0.02         0.13                                             Polybutylacrylate of Example 1                                                                  0.25         0.42                                             phenyl acid phosphate                                                                           0.15         0.2                                              Dodecylbenzene sulfonic acid                                                                    0.75         1.10                                             ______________________________________                                          .sup.1 Acrylic polymer described in footnote 2 of Example 1.                   .sup.2 Linear polyester urethane described in footnote 1 of Example D.   

EXAMPLE 3

A clear film-forming composition containing carbamate functional polyether, acrylic, and cycloaliphatic anhydride-derived polyester polymers was prepared by mixing together the following ingredients:

    ______________________________________                                                          Solid weight Solution weight                                  Ingredient       in grams     in grams                                         ______________________________________                                         Propylene glycol methyl ether                                                                   --           4.8                                              acetate                                                                        SOLVESSO 100     --           9.5                                              oxo-hexyl acetate                                                                               --           10.3                                             n-propanol       --           15.0                                             xylene           --           9.0                                              TINUVIN 328      3.0          3.0                                              AEROSIL R812 dispersion                                                                         5.5          12.5                                             RESIMENE 741     20.0         22.7                                             Anti-sagging agent.sup.1                                                                        0.5          1.4                                              carbamate containing polyether of                                                               15.0         15.0                                             example B                                                                      carbamate containing acrylic                                                                    10.5         16.6                                             polymer of example G                                                           carbamate containing polyester of                                                               49.5         64.5                                             example F                                                                      DOW CORNING 200  0.004        0.74                                             BYK 325          0.02         0.13                                             Dodecylbenzene sulfonic acid                                                                    0.8          1.2                                              ______________________________________                                          .sup.1 Polymeric microparticle prepared in accordance with U.S. Pat. No.       4,147,688, Example 11.                                                   

EXAMPLE 4 (Control)

A clear film-forming composition analogous to Example 3, but containing only hydroxyl functional polymers was prepared by mixing together the following ingredients:

    ______________________________________                                                          Solid weight Solution weight                                  Ingredient       in grams     in grams                                         ______________________________________                                         Propylene glycol methyl ether                                                                   --           4.8                                              acetate                                                                        SOLVESSO 100     --           9.5                                              oxo-hexyl acetate                                                                               --           10.3                                             n-propanol       --           15.0                                             xylene           --           9.0                                              TINUVIN 328      3.0          3.0                                              AEROSIL R812 dispersion                                                                         5.5          12.5                                             RESIMENE 741     20.0         22.7                                             POLYMEG 1000     15.0         15.0                                             Acrylic polymer.sup.1                                                                           10.5         15.0                                             Polyester urethane polyol.sup.2                                                                 49.5         55.0                                             DOW CORNING 200  0.004        0.74                                             BYK 325          0.02         0.13                                             Anti-sagging agent                                                                              0.5          1.4                                              Dodecylbenzene sulfonic acid                                                                    0.8          1.2                                              ______________________________________                                          .sup.1 Acrylic polymer described in footnote 2 of Example 1.                   .sup.2 Linear polyester urethane described in footnote 1 of Example D.   

EXAMPLE 5

A clear film-forming composition was prepared as in Example 1, except that the carbamate-containing polyether of Example B was replaced with the carbamate-containing polyether of Example A.

EXAMPLE 6

A clear film-forming composition was prepared as in Example 1, except that the carbamate-containing polyether of Example B was replaced with the carbamate-containing polyether of Example C.

EXAMPLE 7 (Control)

A clear film-forming composition containing only hydroxyl functional polymers was prepared by mixing together the following ingredients:

    ______________________________________                                                           Solid weight                                                                             Solution weight                                    Ingredient        in grams  in grams                                           ______________________________________                                         n-propanol        --        15.1                                               xylene            --        19.5                                               TINUVIN 328       3.0       3.0                                                AEROSIL R812 dispersion                                                                          5.5       12.5                                               Polyester-urethane.sup.1                                                                         41.0      46.0                                               RESIMENE 741      25.0      28.2                                               MR225.sup.2       10.0      15.4                                               Acrylic polymer.sup.3                                                                            9.5       26.4                                               POLYMEG 1000      10.0      10.0                                               DOW CORNING 200   0.004     0.74                                               BYK 325           0.02      0.13                                               TINUVIN 292.sup.4 0.88      0.88                                               Polybutylacrylate of Example 1                                                                   0.25      0.42                                               phenyl acid phosphate                                                                            0.15      0.2                                                Dodecylbenzene sulfonic acid                                                                     0.75      1.10                                               ______________________________________                                          .sup.1 Reaction product of 1,6hexane diol, hexahydrophthalic anhydride,        neopentyl glycol, and DESMODUR W (an aliphatic diisocyanate available fro      Miles, Inc.) in a 1:1.2:1:0.73 mole ratio, having a hydroxyl value of 183      based on weight of resin solids, 90% in DOWANOL PM acetate.                    .sup.2 partially butylated polymeric melamine resin available from             Monsanto Co.                                                                   .sup.3 Acrylic polymer described in footnote 2 of Example 1.                   .sup.4 Sterically hindered tertiary amine light stabilizer available from      Ciba Geigy Corporation.                                                  

Thermoplastic polyolefin test substrates available from Himont Advanced Materials as ETA-3183 were prepared for coating and acid etch testing by first spray applying a solventborne adhesion promoter available from PPG Industries, Inc., as MPP4110 to the substrate at a thickness of 0.25 mils at ambient atmospheric conditions. The resulting film was dried at ambient atmospheric conditions for two minutes. The promoter was then immediately coated with 1.0 mils of a solventborne elastomeric pigmented base coat composition, commercially available from PPG Industries, Inc. and identified as CBC-7517C. The clear film-forming compositions of examples 1 to 7 were then applied separately wet-on-wet at a thickness of 1.6 mils to seven base coated substrates.

The resultant composite coatings were cured at 250° F. (121.1° C.) for 30 minutes to cure both the base coat and clear coat. The panels were baked in a horizontal position. The properties of the composite coatings are reported in Table I below.

                                      TABLE I                                      __________________________________________________________________________           % OH Functional Resin                                                                     Hydroxyl Number of                                                  Based on Weight of                                                                        Composition Based on                                                                     Acid Etch                                                                           Acid Etch                                      Example                                                                              Resin Solids.sup.1                                                                        Weight of Resin Solids                                                                   Rating.sup.2                                                                        Rating.sup.3                                                                        Cold Flex.sup.4                           __________________________________________________________________________     1     4.5        8         2    3    10                                        2 (Control)                                                                          65         96        8    9    10                                        3     4.5        8         2    2     8                                        4 (Control)                                                                          79.5       118       8    9    10                                        5     4.5        8         3    3    9+                                        6     4.5        8         2    3    10                                        7 (Control)                                                                          69.5       111       9    9    10                                        __________________________________________________________________________      .sup.1 Note that all the compositions had at least 4.5% OH functionality       by weight, due to the acrylic polymer (see footnote 2 of Example 1) added      to the formulation.                                                            .sup.2 After 30 minutes at 110° F. (37.7° C.)                    .sup.3 After 30 minutes at 180° F. (82.2° C.)                    .sup.2,3 Test panels were made in triplicate and spotted four times with       0.2 ml of a sulfurous acid solution (350 grams deionized water and 12          grams sulfurous acid to give a pH of 2.0 plus or minus 0.1) using a 23         gauge syringe. The panels, with drops uncovered, were then placed in           electric ovens at 110° F. (43.3° C.) and at 180° F.       (82.2° C.) for 30 minutes. The panels were removed from the ovens       and were washed with soap and water and dried, then rated for degree of        acid etch resistance on a scale of 1-10 (1 = no observable etching; 10 =       severe etching).                                                               .sup.4 Brittleness of the colorplus-clear composite coating over primed        RIM (Reaction Injection Molding) substrate was tested using General Motor      specification 9503P. The coated plastic substrate was cooled to 0°      F. (-17.8° C.) and bent around a halfinch (1.27 cm) mandrel. A          value below 8 on a scale of 1 to 10 is considered unacceptable (poor           flex). A value of 10 indicates no cracking of the composite coating.     

The data in Table I illustrate the improved acid etch resistant properties of the composition of the present invention when compared to conventional hydroxyl-aminoplast coating compositions. Note that flexibility is maintained.

EXAMPLE 8

A clear film-forming composition containing a carbamate functional polyester polymer derived from a cycloaliphatic anhydride was prepared by mixing together the following ingredients:

    ______________________________________                                                           Solid weight                                                                               Solution weight                                  Ingredient        in grams    in grams                                         ______________________________________                                         n-butanol         --          15                                               2-butoxyethyl ester of acetic acid                                                               --          5                                                xylene            --          15                                               DOWANOL PM        --          10                                               n-propanol        --          5                                                TINUVIN 328       3.0         3.0                                              AEROSIL R812 dispersion                                                                          5.5         12.5                                             RESIMENE 741      20.0        23.0                                             Carbamate containing polyether of                                                                20          20                                               Example B                                                                      DOW CORNING 200   0.004       0.74                                             BAYSILONE OL-17 fluid.sup.1                                                                      --          0.15                                             Polybutylacrylate of Example 1                                                                   0.25        0.42                                             Dodecylbenzene sulfonic acid                                                                     0.75        1.10                                             Carbamate containing acrylic                                                                     10.5        18.04                                            polymer of Example G                                                           Carbamate containing polyester of                                                                45          63                                               Example F                                                                      ______________________________________                                          .sup.1 Polyether polysiloxane fluid, available from Bayer USA.           

EXAMPLE 9

A clear film-forming composition containing a carbamate functional polyester polymer was prepared as in Example 8, except that the carbamate containing polyester derived from a cycloaliphatic acid of Example F was replaced by the carbamate containing polyester derived from a linear acid of Example H.

EXAMPLE 10

A clear film-forming composition formulated without carbamate-functional acrylic was prepared by mixing together the following ingredients:

    ______________________________________                                                       Solid weight    Solution weight                                  Ingredient    in grams        in grams                                         ______________________________________                                         n-butanol     --              49.5                                             2-butoxyethyl                                                                  acetate       --              16.5                                             xylene        --              49.5                                             propylene glycol mono-                                                         methyl ether  --              33.0                                             n-propanol    --              16.5                                             TINUVIN 328   9.9             39.6                                             AEROSIL 812                                                                    dispersion    18.2            42.9                                             RESIMENE 741  66.0            75.9                                             carbamate containing                                                           polyether of                                                                   example B     66.0            66.0                                             DOW CORNING 200               2.4                                              BAYSILONE OL-17               0.5                                              polybutylacrylate of                                                           example 1     0.83            1.39                                             dodecylbenzene                                                                 sulfonic acid 2.6             3.63                                             carbamate containing                                                           polyester of                                                                   Example I     183.2           258.4                                            ______________________________________                                    

Thermoplastic polyolefin test substrates available from D & S Plastics Co. as TPO 880 were prepared for coating as were those used in Examples 1 to 7. The base coat composition used is commercially available from PPG Industries, Inc. and identified as CBC-1855C. The clear film-forming compositions of Examples 8 to 10 were then applied separately wet-on-wet at a thickness of approximately 2 mils (50.8 microns) to three base-coated substrates.

The resultant composite coatings were cured as were the compositions of Examples 1 to 7. The properties of the composite coatings are reported in Tables II and III below.

                  TABLE II                                                         ______________________________________                                         Example    Jacksonville Etch.sup.1                                                                     Fort Lauderdale Spot.sup.2                             ______________________________________                                         8          1            3                                                      9          10           10                                                     ______________________________________                                         .sup.1 Data was collected at the Jacksonville, Florida PPG atmospheric         test                                                                           site on Blount Island. 4 × 6 inch (10.16 × 15.24 cm) test          specimens are                                                                  mounted on 4 × 12 inch (10.16 × 30.48 cm) aluminum panels and      placed                                                                         horizontally on exposure racks. The above data were collected during           one season from May to September. Topcoat damage at this site is               caused by chemical etching (1 = no observable etching, 10 = spotting           with extensive material loss within a spot failure.)                           .sup.2 Data was collected at the Fort Lauderdale, Florida PPG                  atmospheric                                                                    test site. 4 × 6 inch (10.16 × 15.24 cm) test specimens are        mounted on                                                                     4 × 12 inch (10.16 × 30.48 cm) aluminum panels and exposed         facing                                                                         south at an angle of 5° with no insulation. The above data was          collected                                                                      during one season from May to September. Topcoat damage at this site           is recorded as "spotting" and is caused by solid particle deposits on          the surface (1 = no observable damage, 10 = spotting with hard ion             deposit.)                                                                 

                  TABLE III                                                        ______________________________________                                                                      OUV                                               Example                                                                               Etch (H.sub.2 SO.sub.4).sup.1                                                             Etch (HNO.sub.3).sup.2                                                                    Waterspot.sup.3                                                                        Cold flex.sup.4                           ______________________________________                                         8      2          1          good    9                                         9      3          1          very bad                                                                               10                                        10     2          1          very good                                                                              8                                         ______________________________________                                         .sup.1,2 Test panels were spotted with two superimposed drops of 0.6 N         sulfuric acid and two superimposed drops of 0.6 N nitric acid and              placed in an electric oven at 120 °F. for 30 minutes. The panels        were                                                                           removed from the ovens, rinsed, and evaluated on a 0-4 scale                   (0 = no observable etching, 4 = severe etching).                               .sup.3 Panels were evaluated after 359 hours in a Q-U-V Accelerated            Weathering Tester (The Q Panel Co., Cleveland, Ohio). The panels               were irradiated with UVA-340 bulbs (Q-Panel Co.) at 0.72 W/m.sup.2 /nm         for                                                                            four hours at 70 °C. followed by a four-hour water condensation         cycle                                                                          at 50 °C. The irradiation level was controlled by a SOLAR EYE UV        irradiation controller. The panels were removed from the testing               device, and water spotting evaluated visually as shown above.                  .sup.4 Brittleness of the color-plus-clear composite coating over ESTANE       58130 TPU (available from B.F. Goodrich Company) was tested by                 cooling the coated plastic substrate to 0 °F. (-17 °C.) for      24 hours                                                                       and bending it over a 1 inch (2.54 cm) mandrel. See footnote 4 of              Table 1 for rating scale.                                                 

The data in Table II indicate that coating compositions containing polyesters derived from cycloaliphatic diacids (Example 8) are much more durable with respect to outdoor exposure than are compositions containing polyesters derived from linear diacids (Example 9). Note, however, that polyesters derived from lower alkyl linear diacids such as adipic acid are preferred for durability over polyesters derived from higher alkyl diacids such as sebacic acid, which was used in the coating composition in Example 9. The polyester used in the composition of Example 9 provides exceptional flexibility and acid etch resistance, as is shown in Table III.

Data in Table III indicate that compositions of the present invention demonstrate excellent acid etch resistance and flexibility, although the composition containing the polyester derived from sebacic acid (Example 9) had poor waterspot resistance. 

We claim:
 1. A flexible, curable film-forming composition comprising (i) a polyether polymer containing a plurality of terminal or pendant carbamate groups of the structure: ##STR6## wherein said polyether polymer has on average up to two of said terminal or pendant carbamate groups per molecule and wherein said polyether polymer has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups and wherein the polyether polymer is present in the film-forming composition in amounts of 5 to 40 percent by weight based on weight of resin solids in the film-forming composition;(ii) a polymer selected from the group consisting of a polyester polymer present in the film-forming composition in amounts up to 60 percent by weight based on the weight of resin solids in the film-forming composition, a polyurethane polymer, and an acrylic polymer, wherein the latter two can be present in the film-forming composition in amounts of 5 to 50 percent by weight based on weight of resin solids in the film-forming composition and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR7## and wherein each polymer of component (ii) has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups; and (iii) an aminoplast crosslinking agent containing methylol and/or methylol ether groups wherein the aminoplast is present in the film-forming composition in amounts of 15 to 50 percent based on weight of resin solids in the film-forming composition and wherein the equivalent ratio of said pendant or terminal groups to methylol or methylol ether groups is from 0.5 to 2:1 and is sufficient to form a crosslinked film.
 2. The film-forming composition of claim 1 wherein said aminoplast is a condensate of melamine with formaldehyde and optionally an alcohol containing from 1 to 4 carbon atoms.
 3. The film-forming composition of claim 1 wherein the polyether polymer is present in the film-forming composition in amounts of 10 to 30 percent by weight based on weight of resin solids in the film-forming composition.
 4. The film-forming composition of claim 1 wherein the polymer or mixture of polymers of component (ii) comprises a polyurethane polymer and the polyurethane polymer is present in the film-forming composition in amounts up to 50 percent by weight based on weight of resin solids in the film-forming composition.
 5. The film-forming composition of claim 1 wherein the polymer or mixture of polymers of component (ii) comprises an acrylic polymer and the acrylic polymer is present in the film-forming composition in amounts up to 50 percent by weight based on weight of resin solids in the film-forming composition.
 6. The film-forming composition of claim 1 wherein said composition is suitable for application over a plastic substrate comprising a flexible thermosetting or thermoplastic material.
 7. The film-forming composition of claim 1 wherein the polymer of component (ii) is a urethane oligomer adduct from the reaction of diisocyanate and hydroxyalkyl carbamate.
 8. A flexible, curable film-forming composition comprising (i) a polyether polymer containing a plurality of terminal or pendant carbamate groups of the structure: ##STR8## present in the film-forming composition in amounts of 5 to 40 percent by weight based on weight of resin solids in the film-forming composition;(ii) a polymer selected from the group consisting of a polyester polymer derived from a cycloaliphatic acid or anhydride, alone or along with a polyurethane polymer or an acrylic polymer, wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR9## and (iii) an aminoplast crosslinking agent containing methylol and/or methylol ether groups.
 9. The film-forming composition of claim 8 wherein said polyether polymer has on average up to two of said terminal or pendant carbamate groups per molecule.
 10. The film-forming composition of claim 8 wherein said polyether polymer has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups.
 11. The film-forming composition of claim 8 wherein the equivalent ratio of said pendant or terminal groups to methylol or methylol ether groups is from 0.5 to 2:1 and is sufficient to form a crosslinked film.
 12. The film-forming composition of claim 8 wherein the aminoplast is present in the film-forming composition in amounts of 15 to 50 percent based on weight of resin solids in the film-forming composition.
 13. The film-forming composition of claim 8 wherein each polymer of component (ii) has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups.
 14. The film-forming composition of claim 8 wherein the polymer or mixture of polymers of component (ii) is present in the film-forming composition in amounts of 5 to 50 percent by weight based on weight of resin solids in the film-forming composition.
 15. The film-forming composition of claim 8 wherein said cycloaliphatic acid or anhydride is selected from the group consisting of hexahydrophthalic acid, hexahydrophthalic anhydride, methylhexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and methylhexahydrophthalic anhydride.
 16. The film-forming composition of claim 8 wherein the polyester polymer of component (ii) is present in the film-forming composition in amounts up to 60 percent by weight based on weight of resin solids in the film-forming composition.
 17. A flexible, curable film-forming composition comprising (i) a polyether polymer containing a plurality of terminal or pendant carbamate groups of the structure: ##STR10## present in the film-forming composition in amounts of 5 to 50 percent by weight based on weight of resin solids in the film-forming composition;(ii) a polymer selected from the group consisting of a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR11## (iii) a polyester polymer derived from a cycloaliphatic acid or anhydride wherein said polyester polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR12## and (iv) an aminoplast crosslinking agent containing methylol and/or methylol ether groups.
 18. The film-forming composition of claim 17 wherein said cycloaliphatic acid or anhydride is selected from the group consisting of hexahydrophthalic acid, hexahydrophthalic anhydride, methylhexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and methylhexahydrophthalic anhydride.
 19. The film-forming composition of claim 17 wherein said polyether polymer has on average up to two of said terminal or pendant carbamate groups per molecule.
 20. The film-forming composition of claim 17 wherein said polyether polymer has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups.
 21. The film-forming composition of claim 17 wherein said aminoplast is a condensate of melamine with formaldehyde and optionally an alcohol containing from 1 to 4 carbon atoms.
 22. The film-forming composition of claim 17 wherein the equivalent ratio of said pendant or terminal groups to methylol or methylol ether groups is from 0.5 to 2:1 and is sufficient to form a crosslinked film.
 23. The film-forming composition of claim 17 wherein the polyether polymer is present in the film-forming composition in amounts of 5 to 40 percent by weight based on weight of resin solids in the film-forming composition.
 24. The film-forming composition of claim 23 wherein the polyether polymer is present in the film-forming composition in amounts of 10 to 30 percent by weight based on weight of resin solids in the film-forming composition.
 25. The film-forming composition of claim 17 wherein the aminoplast is present in the film-forming composition in amounts of 15 to 50 percent based on weight of resin solids in the film-forming composition.
 26. The film-forming composition of claim 17 wherein each polymer of component (ii) has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups.
 27. The film-forming composition of claim 17 wherein each polyester polymer has an equivalent weight of from about 140 to 2500 based on equivalents of said terminal or pendant carbamate groups.
 28. The film-forming composition of claim 17 wherein the polymer or mixture of polymers of component (ii) is present in the film-forming composition in amounts of 5 to 50 percent by weight based on weight of resin solids in the film-forming composition.
 29. The film-forming composition of claim 17 wherein the polyester polymer is present in the film-forming composition in amounts up to 60 percent by weight based on weight of resin solids in the film-forming composition.
 30. The film-forming composition of claim 17 wherein the polymer or mixture of polymers of component (ii) comprises a polyurethane polymer and the polyurethane polymer is present in the film-forming composition in amounts up to 50 percent by weight based on weight of resin solids in the film-forming composition.
 31. The film-forming composition of claim 17 wherein the polymer or mixture of polymers of component (ii) comprises an acrylic polymer and the acrylic polymer is present in the film-forming composition in amounts up to 50 percent by weight based on weight of resin solids in the film-forming composition.
 32. The film-forming composition of claim 17 wherein said composition is suitable for application over a plastic substrate comprising a flexible thermosetting or thermoplastic material.
 33. A method for applying a composite coating to a substrate which comprises applying to the substrate a colored film-forming composition to form a base coat and applying to said base coat a clear film-forming composition to form a transparent top coat over the base coat wherein the clear film-forming composition comprises a flexible, curable film-forming composition comprising (i) a polyether polymer containing a plurality of terminal or pendant carbamate groups of the structure: ##STR13## present in the film-forming composition in amounts of 5 to 50 percent by weight based on weight of resin solids in the film-forming composition;(ii) a polymer selected from the group consisting of a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR14## (iii) a polyester polymer derived from a cycloaliphatic acid or anhydride wherein said polyester polymer contains a plurality of terminal or pendant carbamate groups of the structure: ##STR15## and (iv) an aminoplast crosslinking agent containing methylol and/or methylol ether groups.
 34. The method of claim 33 wherein the substrate is a plastic substrate comprising a flexible thermosetting or thermoplastic material.
 35. The method of claim 33 wherein the substrate is selected from the group consisting of polyethylene, polypropylene, thermoplastic urethane, polycarbonate, thermosetting sheet molding compound, reaction-injection molding compound, acrylonitrile-based materials, and nylon. 